Low
No protection needed
If you plan to spend some time outdoors in Philadelphia, Pennsylvania, it's a good idea to check the UV Index before going outside. Although the temperature may seem mild, particularly in spring or fall, this does not mean that the level of UV radiation is low.
The Philadelphia UV Index gives a measure of the intensity of ultraviolet radiation from the sun at the Earth's surface. The higher the index, the more quickly unprotected skin can be affected. UV conditions are not uniform throughout the day; they typically increase in the morning, peak about midway through the day, and then become weaker as the afternoon goes on.
The fact that the seasons in Philadelphia change means that the UV forecast is especially useful. In spring the days get longer and the sun rises higher bit by bit, which causes the UV levels to rise quickly as the season moves on. By the end of spring and into summer, days that are sunny can lead to high UV levels at midday. Even on a nice day when it doesn't seem particularly hot, spending several hours outside can result in a considerable amount of sun exposure.
Philadelphia is also most alive outside in the summer. One might walk through Old City, take in the historic area, relax in Fairmount Park, cycle along the Schuylkill River or have a seat outside at a café. It's simple to forget how much time has passed when one is having fun in the city, so it's useful to know the UV level for the day before setting out.
You shouldn't base your judgment of the sun just on the temperature or the presence of clouds, since a cooler day can still have strong UV radiation and cloud cover doesn't always mean that there's no UV exposure. If you'd like to know the UV Index in Philadelphia today, it's better to check the actual forecast rather than just looking at the sky.
The hourly forecast is particularly useful when making arrangements for outdoor activities. In Philadelphia the hourly UV Index shows how the conditions are expected to change from the morning through to the evening. Should you have some flexibility, it might be better to plan your activities outside the strongest part of the midday, since UV radiation is usually lower both in the early part of the day and later on.
The situation is different in winter. Philadelphia generally experiences much lower levels of UV radiation during the colder months since the sun is lower in the sky and the days are shorter. Yet UV radiation is still there, especially on bright, clear days. When spring comes, the levels increase gradually once more.
When the UV Index is high, there are a few simple habits you can follow. Whenever you can, look for shade, wear sunglasses and clothing which covers any exposed skin, and apply broad-spectrum sunscreen to those parts of your body that are not covered. This is especially useful if you are going to be outside for several hours.
The Philadelphia UV Index today is also useful for planning ordinary activities, not just outdoor excursions. Simple activities such as taking a morning walk, having lunch outside, visiting the park, going sightseeing, gardening or attending a sporting event can all result in more time spent in the sun than anticipated.
Before you leave, take a look at the current Philadelphia UV Index and hourly UV forecast. By looking at the conditions quickly, you'll be able to work out when to go out, how long to remain outside, and what type of sun protection to take with you.